The invention relates to a solenoid plunger magnet and to its use as a print hammer in a print hammer device.
FIG. 1 shows a solenoid plunger magnet 5 as it is known from the early days of the magnetism art in the form of a blunt solenoid plunger 1 which is pulled against a flat counter-pole 2 of a yoke 3. The working air gap 4 of this solenoid plunger magnet 5 equals the length of travel of solenoid plunger 1. The result is a steeply rising tractive force curve which, particularly for long travel paths, becomes so weak at the beginning, that it is hardly possible anymore to utilize it. Furthermore, the solenoid plunger magnet 5 also has a second air gap 6, also called the loss air gap since it contributes nothing to the thrust of solenoid plunger 1. The high striking force of solenoid plunger 1 against counter-pole 2 also inevitably reduces its service life.
Therefore, the configuration of the air gaps so as to realize a maximum of performance and service life is very decisive. By appropriately designing the geometry of the plunger and of the counter-poles, it is possible to influence the characteristics over a broad range and thus to adapt them to the intended purpose. For this reason, the operating air gap is configured according to the desired lines of magnetic flux while the loss gap is configured in such a manner that it has the lowest possible magnetic resistance but does not generate forces which move in the direction toward solenoid plunger 1.
DE-OS 2,636,985 discloses a solenoid plunger system in which the second air ga is also utilized to generate magnetic forces. However, the configuration of the outer air gap disclosed there is not meaningful because it doubles the overall air gap length and thus results in a reduction of magnetic flux and a reduction of the magnetic forces in the first air gap, the working air gap.